A top U.S. official is raising serious concerns that a new international plan to deposit some $8 billion directly into accounts controlled by Afghan President Hamid Karzai's team will be ravaged by rampant corruption.

"Pervasive corruption may divert a large portion of this money from its intended uses," warned John Sopko, the special inspector general for Afghanistan reconstruction. Speaking to a Washington group on Wednesday, Sopko added that he has evidence the Afghan government has robbed bank accounts and refused to prosecute high ranking officials accused of corruption.

In the past, U.S. and international funds have been filtered through grants and agencies not tied to Karzai, but the U.S. and other governments have changed that. In July 2012, they agreed to fork over another $16 billion through 2016, and half, or $8 billion, will be deposited directly into Afghan government accounts to spend on what they want.

Sopko's auditors have detailed massive losses of U.S. aid and corruption in several departments responsible for helping rebuild the war-torn nation with American tax dollars.

So far the U.S. has spent more than $54 billion on the reconstruction effort, mostly to train and equip the Afghan national security forces. But Sopko said Afghanistan might not be able to pay for it all. He explained that it will cost up to $10 billion a year to run everything the international community has set up but that Afghanistan only collects $2 billion in revenue annually.

Worse, he said that the government can't even manage it's lucrative customs control. "Some customs offices reportedly lose 70 percent of potential government revenue due to corruption," said Sopko. And, he added, VIPs don't even have to clear customs.

He recommended that the U.S. demand more transparency in how Afghanistan spends aid. And if it can't quell corruption, he wants the funding spigot turned off. "We are negotiating from a position of strength," said Sopko, who in the past has been urged to ease off on his criticism of Afghanistan. "We are giving the Afghans the money. We are in a position to insist on attaching strings to direct assistance — and those strings should bind the Afghans to strong internal controls and U.S. government oversight on how the U.S. taxpayers money is spent."